For the purpose of preventing intrusion of foreign matters such as dust into the joint and leakage of grease sealed in the joint, a bellows-like boot is attached to a constant velocity universal joint used for power transmission in automobiles and various industrial machines. The following are known as a material for the boot for a constant velocity universal joint: a silicone material, a chloroprene (CR) material, an ethylene-acrylic rubber (VAMAC) material, a chlorinated polyethylene (CM) material, or the like.
The constant velocity universal joint includes a plunging type constant velocity universal joint and a fixed type constant velocity universal joint. The plunging type constant velocity universal allows displacement in an axial direction and displacement of an operating angle, and the fixed type constant velocity universal joint allows only the displacement of the operating angle. For example, as illustrated in FIG. 6, a tripod type constant velocity universal joint serving as the plunging type constant velocity universal joint includes, as main components, an outer ring 1 serving as an outer joint member, a tripod member 2 serving as an inner joint member, and rollers 3 serving as torque transmitting members.
The outer joint member 1 includes a mouth portion 5 and a stem portion (not shown). The mouth portion 5 is formed into a cup shape opening to the side opposite to the stem portion, and has an inner surface in which track grooves 6 are arranged and formed along its circumferential direction at 120° pitches.
The tripod member 2 is constituted by a boss 8 and leg shafts 9. In the boss 8, there is formed a spline or a serration hole 61 which is coupled with a shaft 10 so as to transmit torque. The leg shafts 9 protrude from three equiangular positions of the boss 8 in a radial direction. The leg shafts 9 of the tripod member 2 support the rollers 3, respectively.
A boot 15 has a larger-diameter portion 16 to be fixed to the outer ring 1, a smaller-diameter portion 17 to be fixed to the shaft 10 coupled to the tripod member 2, and a bellows portion 18 provided between the larger-diameter portion 16 and the smaller-diameter portion 17. Further, each of the larger-diameter portion 16 and the smaller-diameter portion 17 is fixed by a boot band 20 attached therealong (see Patent Literature 1). Note that the bellows portion 18 is constituted by valley portions 18b and peak portions 18a formed alternately therein.
At the end portion on the opening side of the outer surface of the outer ring 1, a boot-fitting recessed portion 21 is provided, and the radially-inner portion of the larger-diameter portion 16 fits in the boot-fitting recessed portion 21. In this state, the boot band 20 is fitted in a band-fitting groove 22 formed along the radially-outer surface of the larger-diameter portion 16 so as to be attached thereon. As a result, the larger-diameter portion 16 of the boot 15 is fixed onto the outer ring 1.
Further, the shaft 10 is provided with, at a position protruding from the tripod member 2 by a predetermined amount, a boot-fitting portion 24 having a boot-fitting groove 23 formed along the circumferential direction, and the smaller-diameter portion 17 is externally fitted onto the boot-fitting portion 24. Then, the boot band 20 is fitted into a fitting groove 25 formed along the outer peripheral surface of the smaller-diameter portion 17 of the boot 15, to thereby fix the smaller diameter portion 17 to the shaft 10.
As the boot band, a so-called one-touch band and a low profile band are exemplified.
The boot band 20 called one-touch band is, as illustrated in FIG. 7, a band member 30 formed of a band-like metal material, which is curved like a ring and whose both ends are superimposed on one another so as to be engaged with each other. A lever member 32 is adhered to one of superimposed portions 31 of the band member 30.
When the smaller-diameter portion 17 of the boot 15 is mounted onto the shaft 10 with use of the boot band 20, the ring-like band member 30 is first loosely fitted onto the fitting groove 25 of the smaller-diameter portion 17 of the boot 15, and then the lever member 32 is folded back in this state using leverage. As a result, as illustrated in FIG. 8, the band member 30 fitted into the fitting groove 25 of the smaller diameter portion 17 of the boot 15 is decreased in diameter, to thereby clamp the smaller-diameter portion 17 of the boot 15. Note that the end portion of the lever member 32 is engaged by a stopper 33 (see FIG. 7) arranged in the vicinity of the superimposed portion 31.
The low profile band is formed of an annular body. The low profile band is fitted into the fitting groove 25 or the like formed along the outer peripheral surface of the smaller-diameter portion 17, and then decreased in diameter so that the smaller-diameter portion 17 is clamped.